This invention pertains to unique techniques for evaluating the effectiveness or wear efficacy of protective overcoats applied to thin film magnetic disk media. In particular, the invention relates to such techniques as applied to the evaluation of protective carbon overcoat layers which are sputter deposited upon thin film magnetic media in the presence of hydrogen.
To a substantial extent, the success of commercial product ventures is determined by the ability of manufacturers to maintain adequate product performance parameters or standards.
In order to achieve such objectives, manufacturers traditionally rely upon extensive testing and evaluation procedures. Such tend to become costly and can add significantly to the market costs of products.
Incremental additions of cost relating to product testing for adequacy purposes can adversely impact the competitive strength or position of the product manufacturer. In addition, or alternatively, such costs can become a cost increase burden to be borne by the consumer.
In any event, in highly competitive markets, such as those involving the manufacture of thin film magnetic disk media, both customer and competitive considerations require that high quality products be produced with maximum cost efficiency.
The present invention is directed to a particularly successful effort to deal with the evaluation of acceptable operational parameters for magnetic media of the sputtered, thin film type, particularly such which are provided with protective carbon overcoat layers.
This invention affords a unique recognition of the manner in which simple, conventional electrical measurement techniques may be utilized, in a surprising yet efficient manner, to evaluate the mechanical, wear resistant properties of magnetic media, thin film overcoats, such as those provided by carbon applied by sputter coating techniques to previously sputtered magnetic media layers. Preferably, the carbon is sputtered in the presence of hydrogen so as to effect hydrogenation of the carbon overcoat layer.
Such hydrogenation is desired for the purpose of improving the hardness of the applied carbon overcoat and thus improving its wear resistance.
This invention entails three distinct, but to some extent overlapping, aspects as follows:
A. A first, broad, generic aspect entailing the utilization of electrical surface resistance measurements, performed on the exposed outer surface of magnetic media protective overcoat layers so as to afford an empirical indication of adequate hardness or wear surface characteristics; PA1 B. A second aspect, by virtue of which the measurement of electrical resistance of the exposed outer surface of a protective overcoat layer such as carbon, sputtered in the presence of hydrogen, functions to provide an empirical indication of the degree of hydrogenation or acceptable hardness of the sputtered overcoat layer; and/or PA1 C. A third aspect, by virtue of which the measurement of electrical resistance of the exposed outer surface of a protective overcoat layer, such as sputtered carbon, is employed to provide an empirical indication of the degree or presence of abnormally high peaking of generally isolated, elevated, peak like configurations of sputtered carbon (this phenomena will be hereinafter referred to as "peaking density", i.e., a measurement of the extent to which unusually high or elevated carbon, point-like configurations are formed during the sputtering process and which project above the normal roughened surface provided by the carbon sputtering operation. Such "peaks" provide potential interference with the magnetic read/write head which is employed to read or write data in relation to the protected media. PA1 providing a disk substrate; PA1 sputter depositing thin film magnetic media layer means on the substrate; PA1 depositing an overcoat layer over the magnetic media thin film means; PA1 causing spaced electrical probes to engage spaced portions of an exposed outer surface of the carbon overcoat; PA1 creating a voltage across the spaced electrical probes; PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surface of the carbon overcoat; PA1 the measured resistance being a function of the wear properties of said overcoat layer; and PA1 empirically determining, in response to the aforesaid measured resistance, a commercially acceptable wear property of the overcoat layer. PA1 providing a disk substrate, PA1 sputter depositing thin film magnetic media layer means on the substrate, and PA1 sputter depositing an overcoat layer over said magnetic media thin film means. PA1 causing spaced electrical probes to engage spaced portions of an exposed outer surface of the overcoat layer; PA1 creating a voltage across the spaced electrodes; PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surface of the overcoat layer; and PA1 employing the measured resistance generally as a measure of wear properties of said overcoat layer. PA1 providing a disk substrate; PA1 sputter depositing thin film magnetic media layer means on the substrate; PA1 sputter depositing a carbon overcoat over the magnetic media thin film means in the presence of hydrogen; PA1 causing spaced electrical probes to engage spaced portions of an exposed outer surface of the carbon overcoat; PA1 creating a voltage across the spaced electrical probes; PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surface of said carbon overcoat; PA1 empirically determining, in response to the measured resistance, a commercially acceptable degree of hydrogenation of said carbon overcoat. PA1 providing a disk substrate, PA1 sputter depositing thin film magnetic media layer means on the substrate, and PA1 sputter depositing a carbon overcoat over the magnetic media thin film means in the presence of hydrogen. PA1 causing spaced electrical probes to engage spaced portions of an exposed outer surface of the carbon overcoat; PA1 creating a voltage across the spaced electrodes; PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surface of the carbon overcoat; and PA1 employing the measured resistance generally as a measure of hydrogenation of the carbon overcoat. PA1 providing a disk substrate; PA1 sputter depositing thin film magnetic media layer means on the substrate; PA1 sputter depositing a carbon overcoat over the magnetic media thin film layer means; PA1 prior to the completion of the manufacturing method, providing surface roughness on the exposed outer surface of the deposited carbon overcoat; PA1 causing spaced electrical probes to engage spaced portions of the exposed outer surface of the carbon overcoat; PA1 creating a voltage across the spaced electrical probes; PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surface of the carbon overcoat; PA1 empirically determining, in response to the measured resistance, a commercially acceptable degree of surface texturing of the carbon overcoat. PA1 providing a disk substrate; PA1 sputter depositing thin film magnetic media layer means on this substrate; PA1 sputter depositing a protective overcoat over the magnetic media thin film means; PA1 this manufacturing method, prior to the completion thereof, being operable to provide surface roughness on the exposed outer surface of the deposited protective overcoat; PA1 causing spaced electrical probes to engage spaced portions of the exposed outer surface of the protective overcoat; PA1 creating a voltage across the spaced electrical probes; PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surfaces of the protective overcoat; PA1 the measured resistance function being a function of peaking density of the protective overcoat; and PA1 empirically determining, in response to this measured resistance function, a commercially acceptable degree of surface texturing of said protective overcoat. PA1 causing spaced electrical probes to engage spaced portions of an exposed outer surface of a media disk; PA1 creating a voltage across the spaced electrode probes; and PA1 measuring a function of electrical resistance between the ends of the probes in engagement with the exposed outer surface of the disk media; PA1 the measured resistance function being employed as a function of outer surface roughness of the media disk.
The first aspect of the invention, i.e., the generic aspect, is characterized as follows, first with respect to overall manufacturing considerations and second with respect to the product evaluation step itself related to the use of electrical resistance to provide an empirical indication of surface characteristics such as acceptable hardness, peak density, etc.
As to the overall manufacturing operation, this first method aspect may be characterized as follows:
A method is provided for empirically determining the protective characteristics of an overcoat layer for thin film magnetic media disks, this method comprising:
With respect to the resistance measuring step of the generic aspect of the invention, this step may be viewed in the following format:
At the outset, a method is afforded for manufacturing thin film magnetic media disks, which method comprises
The improvement in this method, provided by a first aspect of this invention comprises:
With respect to the second aspect of the invention (i.e., the utilization of surface resistance to provide an indication of the degree of hydrogenation of the protective overcoat, preferably sputtered carbon), the invention again may be considered from the standpoint of the overall manufacturing operation, and from the standpoint of the step involved in the resistance measurement hydrogenation evaluation itself.
With respect to the former, this aspect of the invention is defined in the following form:
A method for empirically determining the degree of hydrogenation of a protective carbon coating for thin film magnetic media disks, this method comprising:
this measured resistance function being an indicator of the degree of hydrogenation of the carbon overcoat; and PA2 this measured resistance being a function of peaking density of the carbon overcoat; and
With respect to the resistance measurement/hydrogenation evaluation step of this second aspect of the invention, the following format is presented:
To begin with, a method for manufacturing thin film magnetic media disks, is provided which comprises
The improvement of this invention in this method comprises:
The third aspect of the invention, relating to the use of electrical resistance measurements on the exposed outer surface of the protective layer overlying thin film magnetic disk media to provide an indication of peaking density, etc., may also be considered in multiple formats as follows.
With respect to overall manufacturing, this third aspect of the invention may be considered as follows:
A method is provided for empirically determining acceptable surface roughness characteristics of thin film magnetic media disks, this method comprising:
Again, in the context of overall manufacturing, but focusing specifically upon peaking density indications of the sputtered carbon overcoat, the following presentation of the invention is applicable.
A method for empirically determining acceptable surface roughness characteristics of thin film magnetic media disks is provided, which method comprising:
With respect to the resistance measurement step itself being employed as an empirical indication of acceptable surface roughness and/or peak density characteristics, the following is applicable:
A method is contemplated for empirically determining acceptable surface roughness characteristics of thin film magnetic media disks, this method comprising:
Any or all of the foregoing aspects of the invention are considered to entail particularly advantageous characteristics in the context of evaluation of a sputtered carbon overcoat applied in the presence of hydrogen.
Moreover, an enhancement of individual aspects of the invention, as heretofore presented, is achieved through the application of uniform pressure to the probes employed to engage wear resistance surface or overcoats for the purpose of making electrical resistance measurements. Preferably such uniform pressure entails not only the application of uniform final pressure, but the application of uniform rates of application of probe pressure as well.